FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
AIR CONDITIONER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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DESCRIPTION
TECHNICAL FIELD
[0001] The present disclosure relates to an air conditioner.
5 BACKGROUND ART
[0002] Introduction of a refrigerant mixture has been studied for the purpose of
reducing refrigerant's global warming potential (GWP). Refrigerant mixture
comprises an azeotropic refrigerant mixture and a non-azeotropic refrigerant mixture.
Japanese Patent Application Laying-Open No. 2016-124474 discloses using a non10 azeotropic refrigerant mixture having a saturation temperature increasing as dryness
increases.
CITATION LIST
PATENT LITERATURE
[0003] [PTL. 1] Japanese Patent Laying-Open No. 2016-124474
15 SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0004] In contrast to a single refrigerant, a non-azeotropic refrigerant mixture has an
evaporation temperature varying during a constant-pressure evaporation process even
in a two-phase region, and thus presents a so-called temperature gradient.
20 [0005] Let us consider an indoor heat exchanger in an air conditioner in which a
cooling operation and a heating operation can be switched by a four-way valve. When
the cooling operation and the heating operation are switched by the four-way valve
alone, then, from a viewpoint in performance of a heat exchanger, it is normally
configured that, in an indoor heat exchanger, refrigerant and air flow in opposite
25 directions in the heating operation and flow in parallel directions in the cooling
operation.
[0006] When a non-azeotropic refrigerant mixture is used in an air conditioner having
such a configuration, an evaporator has a refrigerant inlet port temperature lower than a
refrigerant outlet port temperature due to a temperature gradient. Depending on the
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air blowing temperature and the room temperature, the evaporator may have an inlet
port temperature falling to 0°C or lower, and there is a possibility that frost may form
on the side of the refrigerant inlet port of the heat exchanger of the indoor unit during
the cooling operation.
5 [0007] The present disclosure has been made to address the above-described issue, and
discloses an air conditioner which reduces a possibility of frosting.
SOLUTION TO PROBLEM
[0008] The present disclosure relates to an air conditioner. The air conditioner
comprises: a refrigerant circuit configured to circulate refrigerant through a compressor,
10 a condenser, an expansion valve and an evaporator; a first temperature sensor
configured to sense the temperature of liquid refrigerant at an inlet port of the
evaporator; and a controller configured to control the compressor and the expansion
valve. In a case where the temperature sensed by the first temperature sensor is lower
than a frosting reference temperature, the controller is configured to increase an
15 opening degree of the expansion valve and increase an operating frequency of the
compressor as compared with a case where the temperature sensed by the first
temperature sensor is higher than the frosting reference temperature.
ADVANTAGEOUS EFFECTS OF INVENTION
[0009] The presently disclosed air conditioner can reduce a possibility that the
20 evaporator frosts by adjusting the opening degree of the expansion valve and the
operating frequency of the compressor.
BRIEF DESCRIPTION OF DRAWINGS
[0010] Fig. 1 is a diagram showing a configuration of an air conditioner according to a
first embodiment.
25 Fig. 2 is a diagram showing a relationship among a position in an indoor unit, a
temperature of air, and a temperature of refrigerant.
Fig. 3 is a P-H line diagram of the air conditioner according to the first
embodiment using a non-azeotropic refrigerant mixture.
Fig. 4 is a flowchart for illustrating control executed by a controller 200 in the
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first embodiment.
Fig. 5 is a diagram showing a configuration of an air conditioner 301 according
to a second embodiment.
Fig. 6 is a P-H line diagram when passing through a first channel and that when
5 passing through a second channel.
Fig. 7 is a flowchart for illustrating control executed by controller 200 in the
second embodiment.
DESCRIPTION OF EMBODIMENTS
[0011] Hereinafter, embodiments of the present disclosure will be described in detail
10 with reference to the drawings. Hereinafter, while a plurality of embodiments will be
described, the configurations described in the embodiments are intended to be
combined together, as appropriate, in the present application as originally filed. In the
figures, identical or corresponding components are identically denoted and will not be
described redundantly. The figures may show components in a relationship in size
15 different from their actual relationship in size.
[0012] First Embodiment
Fig. 1 is a diagram showing a configuration of an air conditioner according to a
first embodiment. An air conditioner 1 comprises a compressor 10, an indoor heat
exchanger 20, a linear expansion valve (LEV) 111, an outdoor heat exchanger 40, pipes
20 90, 92, 94, 96, 97 and 99, and a four-way valve 100. Four-way valve 100 has ports E
to H.
[0013] Pipe 90 is connected between port H of four-way valve 100 and a port P1 of
indoor heat exchanger 20. Pipe 92 is connected between a port P4 of indoor heat
exchanger 20 and LEV 111. Pipe 94 is connected between LEV 111 and a port P3 of
25 outdoor heat exchanger 40.
[0014] Pipe 96 is connected between a port P2 of outdoor heat exchanger 40 and port F
of four-way valve 100. Pipe 97 is connected between a refrigerant inlet port 10a of
compressor 10 and port E of four-way valve 100. Pipe 99 is connected between a
refrigerant outlet port 10b of compressor 10 and port G of four-way valve 100, and
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provided at some midpoint thereof with a temperature sensor 104 configured to
measure refrigerant temperature.
[0015] Air conditioner 1 further comprises temperature sensors 101 to 103 and a
controller 200. Controller 200 controls compressor 10, four-way valve 100, and LEV
5 111 in response to an operation command signal provided by a user and outputs of
variety of types of sensors.
[0016] Controller 200 comprises a CPU (Central Processing Unit) 201, a memory 202
(ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output
buffer (not shown), and the like. CPU 201 loads a program, which is stored in the
10 ROM, in the RAM or the like and executes the program. The program stored in the
ROM is a program describing a procedure of a process to be performed by controller
200. Controller 200 executes control of each device in air conditioner 1 in accordance
with these programs. This control is not limited to processing by software, and
processing by dedicated hardware (electronic circuity) is also possible.
15 [0017] Compressor 10 is configured to change its operating frequency in response to a
control signal F* received from controller 200. Specifically, compressor 10
incorporates a drive motor inverter-controlled and variable in rotational speed, and
when the operating frequency of compressor 10 is changed, the rotational speed of the
drive motor changes. The output of compressor 10 is adjusted by changing the
20 operating frequency of compressor 10. Compressor 10 may be of various types, for
example, a rotary type, a reciprocating type, a scroll type, a screw type, or the like.
[0018] Four-way valve 100 is controlled by a control signal received from controller
200 to have either a state A (a cooling operation state) or a state B (a heating operation
state). State A is a state with port E and port H in communication and port F and port
25 G in communication. State B is a state with port E and port F in communication and
port H and port G in communication. By operating compressor 10 in state A (or the
cooling operation state), refrigerant circulates through the refrigerant circuit in a
direction indicated by a solid arrow. By operating compressor 10 in state B (or the
heating operation state), refrigerant circulates through the refrigerant circuit in a
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direction indicated by a broken line arrow.
[0019] LEV 111 normally has a degree of opening, as controlled by a control signal
received from controller 200, to adjust SH (superheat: a degree of heating) of
refrigerant at the outlet port of the evaporator.
5 [0020] Further, in the present embodiment, when there is a high possibility of frosting,
LEV 11 is additionally controlled to have a somewhat larger degree of opening than
when the LEV is normally controlled to adjust the SH as described above.
(Alternatively, a thermistor is installed at the inlet port of the indoor heat exchange, and
the opening degree of LEV 11 is adjusted so that the temperature of the thermistor does
10 not fall below 0°C.) This prevents frosting in the vicinity of the refrigerant inlet port
of the indoor unit when there is a high possibility of frosting. And in order to
maintain refrigeration capacity, controller 200 sets the compressor's frequency to be
high so as to achieve a targeted air-blowing temperature.
[0021] Let us consider an indoor heat exchanger under a cooling condition with a non15 azeotropic refrigerant mixture having a temperature gradient.
[0022] Fig. 2 is a diagram showing a relationship among a position in an indoor unit, a
temperature of air, and a temperature of refrigerant. When a single refrigerant is used
with the indoor unit having a low air-blowing temperature for example of X°C, the
refrigerant presents a uniform temperature distribution of (X - ΔT)°C, as indicated in
20 Fig. 2 by a refrigerant temperature Tr0, from the indoor unit's refrigerant inlet port to a
vicinity of its refrigerant outlet port. In a normal cooling operation, air-blowing
temperature X°C is determined by a user's setting of a remote controller or the like. In
a cooling operation, in order to lower an air-blowing temperature to a set temperature,
refrigerant temperature is set to be lower than the set temperature by ΔT°C. When the
25 setting of the air-blowing temperature is lowered, then, in order to ensure a temperature
difference between refrigerant's outlet port temperature and the air-blowing temperature,
LEV 11 is controlled so that the evaporation temperature follows at a temperature
lower than the set temperature by ΔT. Specifically, LEV 11 is controlled to have a
discharging temperature at a target temperature. The target temperature for the
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discharging temperature is determined based on a target temperature for the
evaporation temperature or a target temperature for the air-blowing temperature.
[0023] In contrast, the non-azeotropic refrigerant mixture has an inlet port temperature
lower than an outlet port temperature due to the temperature gradient. When the
5 refrigerant's outlet port temperature is caused to follow the air-blowing temperature, the
refrigerant's inlet port temperature becomes further lower as indicated by a refrigerant
temperature Tr1. Depending on the setting of the air-blowing temperature X°C and
the room temperature, as indicated in Fig. 2 by refrigerant temperature Tr1, the
evaporator's inlet port temperature decreases to be close to 0°C, and there is a
10 possibility that, under a cooling condition, frost may form in a vicinity of the
refrigerant inlet port of the heat exchanger (or evaporator) of the indoor unit.
[0024] For example, in a dehumidifying operation, refrigerant temperature (or
evaporation temperature) is lowered to be lower than in the normal cooling operation to
actively condense indoor air. Therefore, in the dehumidifying operation, an air
15 blowing temperature lower than that in the cooling operation is set. Therefore, ΔT is
set to be large, resulting in a further increased possibility of frosting.
[0025] In order to avoid such frosting in the vicinity of the refrigerant inlet port of the
indoor unit during the cooling operation, in the present embodiment, the control is
changed as follows:
20 [0026] Initially, the temperature difference between the refrigerant outlet and inlet
ports of the indoor unit, that is, the temperature gradient, is reduced. In order to do so,
when there is a high possibility of frosting, LEV 111 is opened more than normal to
reduce an enthalpy difference ΔH between the refrigerant outlet and inlet ports of the
indoor unit and hence a saturation temperature difference between the inlet and outlet
25 ports of the indoor unit (or evaporator). This changes refrigerant temperature from
Tr1 to Tr1A as shown in Fig. 2, and even if a temperature difference ΔT is ensured at
the refrigerant outlet port of the indoor unit, the vicinity of the refrigerant inlet port of
the indoor unit can avoid having a temperature of a negative value.
[0027] However, enthalpy difference ΔH in the evaporator is smaller than normal, and
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accordingly, the operating frequency of compressor 10 is also increased to provide an
increased refrigerant flow rate to ensure refrigeration capacity equivalent to that as
normal.
[0028] Variation of enthalpy difference ΔH will be described below. Fig. 3 is a P-H
5 line diagram of the air conditioner according to the first embodiment using a nonazeotropic refrigerant mixture. Referring to Fig. 3, a broken line P1-P2-P3-P4-P1
indicates a refrigeration cycle when conventional control is executed. In contrast, a
solid line P1A-P2A-P3A-P4A-P1A indicates a refrigeration cycle in the air conditioner
according to the first embodiment.
10 [0029] When LEV 111 is opened more than normal, point P4 of the refrigerant inlet
port of the evaporator moves to point P4A, and point P1 of the refrigerant outlet port
thereof moves to point P1A. As a result, enthalpy difference ΔH decreases.
Accordingly, in order to compensate for the reduction of enthalpy difference ΔH and
maintain the same refrigeration capacity, the operating frequency of compressor 10 is
15 increased to circulate refrigerant in an increased amount.
[0030] Fig. 4 is a flowchart for illustrating control executed by controller 200 in the
first embodiment.
[0031] Referring to Figs. 1 and 4, in step S1, controller 200 determines whether a user
has changed a set temperature via input device 210 or switched on/off a
20 dehumidification mode. When there is no such change in input setting (NO in S1), the
process proceeds to step S8, and input via the input device is awaited again.
[0032] In contrast, when the input setting has been changed (YES in S1), then, in step
S2, controller 200 reads a target temperature T*, which is a set room temperature, from
input device 210, an indoor suction temperature T2 from temperature sensor 102, and
25 an indoor air blowing temperature T3 from temperature sensor 103, and uses these
temperatures to calculate a target temperature T4* for a discharging temperature T4 of
compressor 10.
[0033] Subsequently, in step S3, controller 200 changes the operating frequency of
compressor 10 to adjust the rotational speed of the drive motor of compressor 10 so that
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indoor air-blowing temperature T3 reaches a target temperature T3*. Further,
controller 200 adjusts the opening degree of LEV 111 so that discharging temperature
T4 is target temperature T4*.
[0034] Further, in step S4, controller 200 determines whether indoor heat exchanger 20
5 has a liquid-side temperature T1 smaller than a reference value. The reference value
is, for example, about 0 to 1°C. When temperature T1 is equal to or higher than the
reference value (NO in S4), it is determined that there is no risk of frosting of indoor
heat exchanger 20, and a normal operation is performed in step S5 with the opening
degree of LEV 111 and rotational speed of the drive motor of compressor 10 as
10 determined in step S3.
[0035] In contrast, when temperature T1 is lower than the reference value (YES in S4),
frost may form in the vicinity of the inlet port of indoor heat exchanger 20.
Accordingly, in step S6, controller 200 sets the opening degree of LEV 111 to be larger
than that in the normal operation, or corrects the target value for discharging
15 temperature T4 to be smaller than that in the normal operation.
[0036] Further, in step S7, after controller 200 increases the opening degree of LEV
111 to be larger than that in the normal operation, controller 200 increases the operating
frequency of compressor 10 to increase the rotational speed of the motor so that airblowing temperature T3 reaches the target temperature.
20 [0037] The first embodiment described above will be summarized with reference to the
drawings. Air conditioner shown in Fig. 1 comprises: refrigerant circuit 2 configured
to circulate refrigerant through compressor 10, a condenser (outdoor heat exchanger 40),
LEV 111 and an evaporator (indoor heat exchanger 20); first temperature sensor 101
configured to sense the temperature of liquid refrigerant at the inlet port of the
25 evaporator (indoor heat exchanger 20); and controller 200 configured to control
compressor 10 and LEV 111.
[0038] When temperature T1 sensed by first temperature sensor 101 is lower than the
frosting reference temperature, controller 200 increases the opening degree of LEV 111
and the operating frequency of compressor 10 to be larger than when temperature T1
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sensed by first temperature sensor 101 is higher than the frosting reference temperature.
[0039] Thus increasing the opening degree of LEV 111 can reduce enthalpy difference
ΔH between the refrigerant inlet and outlet ports of the evaporator (indoor heat
exchanger 20), and hence a difference in temperature between the refrigerant inlet and
5 outlet ports of the evaporator (indoor heat exchanger 20), as shown in Fig. 3.
[0040] Such control can prevent temperature T1 on the side of the refrigerant inlet port
of the evaporator (indoor heat exchanger 20) from dropping to a temperature at which
there is a possibility of frosting, and also maintain refrigeration capacity of air
conditioner 1 as it is.
10 [0041] Preferably, when temperature T1 sensed by first temperature sensor 101
changes from a temperature higher than the frosting reference temperature to a
temperature lower than the frosting reference temperature, then, controller 200
increases the opening degree of LEV 111 and thereafter increases the operating
frequency of compressor 10, as indicated in Fig. 4 by steps S6 and S7.
15 [0042] Initially increasing the operating frequency of compressor 10 would increase
refrigeration capacity, and also further decrease the temperature of the refrigerant inlet
port of the evaporator, resulting in an increased possibility of frosting. Therefore, it is
better to initially increase the opening degree of LEV 111 and thereafter increase the
operating frequency of compressor 10.
20 [0043] Preferably, as shown in Fig. 1, air conditioner 1 further comprises second
temperature sensor 102 configured to sense temperature T2 of air flowing toward the
evaporator (indoor heat exchanger 20), third temperature sensor 103 configured to
sense temperature T3 of air flowing from the evaporator (indoor heat exchanger 20),
and input device 210 configured to set target temperature T* for room temperature.
25 When temperature T1 sensed by first temperature sensor 101 is higher than the frosting
reference temperature (NO in S4), controller 200 determines an opening degree for
LEV 111 and an operating frequency for compressor 10 based on temperature T2
sensed by second temperature sensor 102, temperature T3 sensed by third temperature
sensor 103 and target temperature T* (S3), and applies them to a normal operation as
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they are (S5).
[0044] The opening degree of LEV 111 and the operating frequency of compressor 10
thus determined and applied to the normal operation are set to appropriate values from
a viewpoint of reducing power consumption and the like. In contrast, when there is a
5 risk of frosting, an opening degree for LEV 111 and an operating frequency for
compressor 10 for operation are set to reduce ΔH to avoid frosting although such
setting deviates from normal setting.
[0045] Second Embodiment
Fig. 5 is a diagram showing a configuration of an air conditioner 301 according
10 to a second embodiment. Air conditioner 301 comprises a refrigerant circuit 302
instead of refrigerant circuit 2 shown in Fig. 1. As well as refrigerant circuit 2,
refrigerant circuit 302 is also configured to circulate refrigerant through compressor 10,
a condenser (outdoor heat exchanger 40), LEV 111, and an evaporator (indoor heat
exchanger 20).
15 [0046] In addition to the configuration of refrigerant circuit 2 shown in Fig. 1,
refrigerant circuit 302 further comprises a first channel 321 and a second channel 322
provided in parallel between the evaporator (indoor heat exchanger 20) and refrigerant
inlet port 10a of compressor 10, a channel selector 312 configured to selectively pass
refrigerant through one of first channel 321 and second channel 322, and a heat
20 exchanger 310 configured to exchange heat between refrigerant passing through second
channel 322 and refrigerant discharged by compressor 10.
[0047] In Fig. 5, channel selector 312 is configured including a three-way valve 312A
and a three-way valve 312B. However, the configuration of channel selector 312 is
not limited to the configuration shown in Fig. 5. For example, either three-way valve
25 312A or three-way valve 312B may be a simple branching or junction point without a
valve.
[0048] When temperature T1 sensed by first temperature sensor 101 is lower than the
frosting reference temperature, controller 200 increases the opening degree of LEV 111
to be larger and increases the operating frequency of compressor 10 to be larger than in
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the normal operation, than when temperature T1 sensed by first temperature sensor 101
is higher than the frosting reference temperature.
[0049] Together with this, when temperature T1 sensed by first temperature sensor 101
is lower than the frosting reference temperature, controller 200 controls channel
5 selector 312 to select second channel 322.
[0050] In the first embodiment, refrigerant sucked into compressor 10 becomes humid
refrigerant, and compressor 10 deteriorates in reliability. A package air conditioner
has an accumulator, which prevents liquid from returning (back) to compressor 10,
whereas a room air conditioner is often not provided with an accumulator.
10 Accordingly, in the second embodiment, in order to prevent liquid from returning back,
when an operation of decreasing an air-blowing temperature is performed, a path which
allows heat exchange between refrigerant before it is sucked into compressor 10 and
that after it is discharged therefrom is selected as indicated in Fig. 5 by an arrow R2.
[0051] Thus, when there is a risk of frosting, second channel 322 (indicated by arrow
15 R2) that allows heat exchange between refrigerant before it is sucked and refrigerant
after it is discharged can be selected to reduce a temperature difference between the
outlet and inlet ports of the evaporator while preventing liquid from returning back to
the compressor. When there is no concern about frosting, refrigerant is passed
through first channel 321 as indicated by an arrow R1 in order to increase enthalpy
20 difference.
[0052] Fig. 6 is a P-H line diagram when passing through the first channel and that
when passing through the second channel. When first channel 321 shown in Fig. 5 is
selected, refrigerant at the suction port of compressor 10 has a state corresponding to
point P1A, and refrigerant at the discharging port thereof has a state corresponding to
25 point P2A. In contrast, when second channel 322 shown in Fig. 5 is selected, heat
exchanger 310 performs heat exchange, and as a result, point P1A moves to point P1B,
and point P2A moves to point P2B. As a result, point P1A present in a two-phase
region moves to point P1B present in a gas phase region, and there is no concern that
compressor 10 sucks liquid refrigerant.
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[0053] Fig. 7 is a flowchart for illustrating control executed by controller 200 in the
second embodiment. The Fig. 7 flowchart corresponds to the Fig. 4 flowchart plus
steps S11 and S12. The process has a remainder which is identical to that of Fig. 4,
and accordingly, will not be described repeatedly.
5 [0054] In response to NO in step S4, step S11 is performed to control three-way valves
312A and 312B to select second channel 322 (as indicated by arrow R2). In contrast,
in response to YES in step S4, step S12 is performed to control three-way valves 312A
and 312B to select first channel 321 (as indicated by arrow R1).
[0055] The air conditioner according to the second embodiment is configured such that
10 a passage of refrigerant before it is sucked into the compressor is divided into first
channel 321 and second channel 322, and second channel 322 allows heat exchanger
310 to perform heat exchange with discharged refrigerant. In addition to an effect
provided by the air conditioner of the first embodiment, this can prevent liquid from
returning back to compressor 10, and thus enhance reliability.
15 [0056] It should be understood that the embodiments disclosed herein have been
described for the purpose of illustration only and in a non-restrictive manner in any
respect. The scope of the present disclosure is defined by the terms of the claims,
rather than the embodiments description above, and is intended to include any
modifications within the meaning and scope equivalent to the terms of the claims.
20 REFERENCE SIGNS LIST
[0057] 1, 301 air conditioner, 2, 302 refrigerant circuit, 10 compressor, 10a refrigerant
inlet port, 10b refrigerant outlet port, 20 indoor heat exchanger, 40 outdoor heat
exchanger, 90, 92, 94, 96, 97, 99 pipe, 100 four-way valve, 101, 102, 103, 104
temperature sensor, 200 controller, 201 CPU, 202 memory, 210 input device, 310 heat
25 exchanger, 312 channel selector, 312A, 312B three-way valve, 321, 322 channel, E, F,
G, H, P1, P2, P3 port.

WE CLAIM:
1. An air conditioner comprising:
a refrigerant circuit configured to circulate refrigerant through a compressor, a
5 condenser, an expansion valve, and an evaporator;
a first temperature sensor configured to sense a temperature of liquid refrigerant
at an inlet port of the evaporator; and
a controller configured to control the compressor and the expansion valve,
wherein
10 in a case where the temperature sensed by the first temperature sensor is lower
than a frosting reference temperature, the controller is configured to increase an
opening degree of the expansion valve and increase an operating frequency of the
compressor as compared with a case where the temperature sensed by the first
temperature sensor is higher than the frosting reference temperature.
15
2. The air conditioner according to claim 1, wherein when the temperature
sensed by the first temperature sensor changes from a temperature higher than the
frosting reference temperature to a temperature lower than the frosting reference
temperature, the controller is configured to increase the opening degree of the
20 expansion valve and thereafter increase the operating frequency of the compressor.
3. The air conditioner according to claim 1 or 2, further comprising:
a second temperature sensor configured to sense a temperature of air flowing
toward the evaporator;
25 a third temperature sensor configured to sense a temperature of air flowing from
the evaporator; and
an input device configured to set a target temperature for a space to be airconditioned, wherein
when the temperature sensed by the first temperature sensor is higher than the
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frosting reference temperature, the controller is configured to determine the opening
degree of the expansion valve and the operating frequency of the compressor based on
the temperature sensed by the second temperature sensor, the temperature sensed by the
third temperature sensor, and the target temperature.
5
4. The air conditioner according to any one of claims 1 to 3, wherein
the refrigerant circuit comprises
a first channel and a second channel provided in parallel between the
evaporator and a suction port of the compressor,
10 a channel selector configured to selectively pass refrigerant through one
of the first channel and the second channel, and
a heat exchanger configured to exchange heat between refrigerant
passing through the second channel and refrigerant discharged by the compressor, and
when the temperature sensed by the first temperature sensor is lower than the
15 frosting reference temperature, the controller is configured to control the channel
selector to select the second channel.